This application claims priority to German Patent Application 102 16 896.2, filed Apr. 17, 2002, herein incorporated by reference.
The invention relates to aqueous dispersions of polysiloxane-polyurethanes based on selected, substantially difunctional starting materials, to their preparation and use for preparing coating compositions, and to a coating composition comprising as substantial binder component polysiloxane-polyurethanes of the kind mentioned. The coating compositions of the invention are especially suitable for use as soft feel coatings.
Modern aqueous binders are capable in many applications of substituting organically dissolved binders. This is so in particular in those segments where aqueous binders may have specific advantages, such as in electrocoating, for example.
For applications having highly specific requirements, such as the painting or coating of plastics with soft feel effect coating materials, there has to date been a lack of satisfactory aqueous binders which meet the requirements imposed.
The level of properties presented by the organically dissolved soft feel coating materials based on polyurethane (for example, WO-92/1626 or JP-A-279 620 with the publication number J63 132-919-A), particularly in terms of the soft feel effect, the solvent resistance, the mechanical properties of the film and its adhesion to the substrate, is not attained by aqueous systems. In particular, the combination of a good soft feel effect with a satisfactory solvent resistance on the part of the coating is not possible with state of the art aqueous products.
EP-A-578 940 discloses in this respect water-dispersible polyurethanepolyols based on branched polyesterpolyols.
The use of aqueous polyester-polyurethane dispersions is described in EP-A-669 352. Here again, the soft feel effect is achieved only by the addition of special flatting agents to the Polyester-Polyurethane dispersion.
It is therefore an object of the invention to provide aqueous binders suitable for high-elasticity coating materials, coatings and sealants, especially for soft feel coating materials, which combine a good soft feel effect with good film mechanical properties and adhesion and also a satisfactory solvent resistance and which, furthermore, contain volatile organic substances to the smallest possible extent, so as to be able to meet exacting requirements with respect to environmental compatibility as well.
It has been possible to achieve these objects and others with the provision of the aqueous polysiloxane-polyurethane dispersions described in more detail below and of the coating compositions based on said dispersions.